Fluorescent brightening agents are used primarily to complement unwanted yellowish shades of textiles or paper by supplying complementary bluish light in the presence of UV radiation. An important market segment of the solvent soluble fluorescent brighteners is their application in textiles like noncellulosics. The application of solvent soluble fluorescent brighteners such as the coumarines is usually done via aqueous dispersions, thus most solvent soluble fluorescent brighteners are marketed as aqueous dispersions.
Numerous fluorescent brighteners have been formulated into aqueous dispersions and are described in the patent literature, for example U.S. Pat. Nos. 4,216,111, 4,369,040, 4,288,225 and 4,304,569. Many dispersions containing fluorescent brighteners which are commercially available today, especially in Europe, have at most about 10% by weight of the particular brightener utilized. Often, this is not optimal in terms of economics and efficiency. That is, there are considerably more costs associated with producing, shipping and storing relatively unconcentrated aqueous dispersions.
Aminocoumarines like 7-diethylamino, 4-methyl coumarine and 7-dimethylamino, 4-methyl coumarine, often referred to as Fluorescent Brighteners 61 and 130, respectively, are an interesting class of fluorescent brighteners for non-cellulosics. It is believed that these fluorescent brighteners have not been formulated into aqueous dispersions.
A great number of different dispersants have also been utilized with fluorescent brighteners in formulating aqueous dispersions. These dispersants include many anionic, nonionic and cationic polymers. In many instances, the exact formula of these polymers is not known because their exact constitutions are trade secrets. Thus, they are often referred to by their trademarks or trade names/manufacturers.
There presently exists a need for aqueous dispersions with aminocoumarine type fluorescent brighteners such as 7-diethylamino, 4-methyl coumarine and 7-dimethylamino, 4-methyl coumarine in combination with suitable dispersants. There also exists a need for aqueous dispersions which can be made relatively more concentrated in terms of the particular fluorescent brightener utilized.